It's an issue now only because it's a hot topic in Congress. It's like how abortion/stem cell research/etc. become highly debated topics for periods of time, and almost ignored in others- even though the issue is always the same.
And there are hundreds of ISPs, but that's really irrelevent. The telecommunications industry (the infrastructure that the internet runs on), is owned by 4 major corporations- BellSouth, AT&T, Verizon, and Quest. They sell their bandwidth to smaller ISPs who in turn sell it to consumers, so if they choose to limit bandwidth to certain sites, it will be limited regardless of what ISP you are directly buying from.
Congress has been doing a decent job in strengthening network nuetrality. http://www.publicknowledge.org/pdf/hr5417-109.pdf
has been introduced and http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=109_cong_bills&docid=f:h5252ih.txt.pdf
is being revised to be less lenient.
However, many ISPs won't restrict bandwidth because it's already a legal tarpit. And there is a lot of support for Net Neutrality from corperate sites.
"Campaigns have also been launched by content providers (including Google, Microsoft, Yahoo! and Amazon.com) in support of neutrality and regulation ([Don't Mess with the Net]), and by service providers (including AT&T and Verizon) against it.([Hands Off the Internet])" (Wikipedia)